My U.S. Pat. No. 5,642,586 describes a method of improving the growth characteristics of orchid plants which comprises applying to the roots of the plants an aqueous solution containing methanol and a fertilizer. The application of methanol to the orchid plant roots produces earlier flowering and more shoots and increases high temperature tolerance, root vigor, bright light tolerance, and foliage glossiness or shininess.
The present invention is based on the recognition that an aqueous solution containing methanol and a high nitrogen fertilizer applied to the plant roots of a large number of different plant varieties beyond the orchid family produces remarkable growth enhancement of the plants treated with the methanol/high nitrogen fertilizer solution.
The use of methanol for promoting plant growth has been reported throughout the scientific literature in recent years. Perhaps the leading article in the field is authored by Nonomura A. M. and A. A. Benson, 1992, "The Path of Carbon in Photosynthesis: Improved Crop Yields With Methanol," Proc. Natl. Acad. Sci., 89:97 94-97 98, who reported remarkable growth enhancement of C.sub.3 plants treated with methanol. A methanol solution sprayed on the leaves of a variety of C.sub.3 plants such as tomatoes, strawberries, eggplant, cotton, cabbage, wheat, rose, palm and watermelon produced enhanced growth characteristics. Other positive responses to plants treated with methanol also have been reported in the literature. However, more publications relating to this subject have reported no evidence of growth gain. These contradictory results have left the usefulness of methanol treatment unresolved.
A recent article by McGiffen, Jr., M. E. and J. A. Manthey, "The Role of Methanol and Promoting Plant Growth: A Current Evaluation," Hort. Science, Dec. 19, 1996, 31(7): 1092-1096, evaluated a large number of studies and concluded that the overwhelming evidence from the scientific literature is that methanol is not a reliable stimulant to crop productivity; and that although the methods have not been consistent across all of the studies, investigations that duplicated Nonomura and Benson's procedures failed to find consistent increases in crop yield. McGiffen et al. concluded that additional field experiments that simply repeat Nonomura and Benson's protocol are unlikely to provide new insights, and that the foliar application of methanol is unlikely to become a practical yield enhancer.
The present invention is based on the recognition that, contrary to the McGiffen et al. study, methanol can be used to promote plant growth. According to the present invention, a methanol-enhanced aqueous solution of a high nitrogen fertilizer applied to the plant roots produces remarkable improvements in many growth characteristics of C.sub.3 plants. Moreover, such plant growth improvement has been produced in a variety of C.sub.3 plant species including fruits, vegetables, trees and flowering plants. Improved growth in CAM variety plants also has been demonstrated.